1. Field of the Invention
The present invention relates to a liquid jet head which ejects liquid from nozzles to form images and letters on a recording medium or to form a thin film material, and a liquid jet apparatus using the same.
2. Description of the Related Art
In recent years, there has been used an ink jet type liquid jet head which ejects ink droplets onto recording paper and the like to draw letters and diagrams, or ejects a liquid material onto a surface of an element substrate to form a functional thin film. The liquid jet head of this type is supplied with ink or a liquid material from a liquid tank via a supply tube, and is caused to eject the ink or the liquid material filled in channels thereof from nozzles communicated to the channels. At the time of ink ejection, the liquid jet head and a recording medium for recording the jetted liquid are moved, to thereby record the letters and diagrams or form the functional thin film in a predetermined shape.
For example, Japanese Patent Application Laid-open No. 2004-351641 describes the liquid jet head of this type. FIG. 9 is a schematic view illustrating an ink flow path of a printing head 101 described in Japanese Patent Application Laid-open No. 2004-351641 (FIG. 2 of Japanese Patent Application Laid-open No. 2004-351641). At a lower portion of the printing head 101, there are provided an ink ejection nozzle 201 for ejecting ink downwardly and a nozzle liquid chamber 202 for supplying ink to the ink ejection nozzle 201. On a right side of an upper portion of the printing head 101, there are provided an OUT liquid chamber 301 for supplying ink to the nozzle liquid chamber 202 and an IN liquid chamber 204 for supplying ink to the OUT liquid chamber 301 via a head filter 203. The head filter 203 is arranged vertically or at an inclination. Ink sent in a tube 114 under pressure flows into a lower portion of the IN liquid chamber 204, and flows out from an upper portion of the IN liquid chamber 204 to enter a tube 115.
The head filter 203 is provided between the OUT liquid chamber 301 and the IN liquid chamber 204, and the ink circulates via the tube 114, the IN liquid chamber 204, and the tube 115. Further, the OUT liquid chamber 301 is arranged above the nozzle liquid chamber 202. With this structure, air bubbles do not pass through the head filter 203 at the time of cleaning, and are discharged outside together with the ink circulation due to the buoyancy of the air bubbles. Therefore, the flow rate of ink to be used in circulation cleaning can be remarkably reduced as compared to a conventional liquid jet head.
In the above-mentioned conventional example, the head filter 203 provided between the IN liquid chamber 204 and the OUT liquid chamber 301 is provided for removing dust mixed into the ink. However, when the head filter 203 is inserted between an ink inflow portion and the ink ejection nozzle 201, the pressure loss of the ink flowing in the printing head 101 increases, and thus a printing stable zone, which represents a condition range for stable ejection of ink, becomes narrower. For example, a voltage range which enables stable printing becomes narrower. Further, along with the use of the printing head 101, air bubbles adhere to the head filter 203 on the IN liquid chamber 204 side and accumulate in the IN liquid chamber 204. As a result, the effective area of the head filter 203 reduces to cause shortage of ink supply to the nozzle liquid chamber 202 side. Further, the air bubbles accumulated in the IN liquid chamber 204 may pass through the head filter 203 to flow into the nozzle liquid chamber 202, which may cause deterioration of printing quality such as dot missing.